What is the model of your Dell laptop?
It may be it has a older Wifi card that needs updating to the same standard as your wireless network. For instance it will be one of these 802.11 a/b/g/n/ac From a to ac each incrument gives more speed.
For instance my Dell e6540 wireless is n class. I can upgrade it to a newer card that will handle AC but my present wireless network is n class so no advantage.
My Dell laptop downloads at a rate around 13 mgs, whereas my other desktops and mobile devices download at my contracted rate of 40 mgs. What should I do to correct? Thanks